 * {
     margin: 0;
     padding: 0;
 }
@keyframes colorRotate {
    0% {
        filter: hue-rotate(0deg);
    }
    100% {
        filter: hue-rotate(360deg);
    }
}
canvas {
    position: absolute;
    z-index: -1;
    display: block;
    margin: 0 auto;
    background-image: linear-gradient(to bottom, rgb(0, 87, 168), rgb(0, 23, 27));
    animation: colorRotate 2s infinite;
}
.cover,
.over{
    position: absolute;
    width: 100vw;
    height: 100vh;
    background-color: rgba(94, 92, 167,.8);
    text-align: center;
}
.title {
    display: block;
    margin: 50px auto;
}
.rule {
    font-size: 28px;
    color: brown;
    text-align: center;
    text-shadow: -2px -2px 6px brown;
}
.cover button {
    padding: 20px;
    margin: 30px;
    color: rgb(11, 79, 156);
    background-color: coral;
    text-shadow: -2px -2px 6px coral;
    border: none;
    cursor: pointer;
}
.over {
display: none;
}